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Unread 12-08-2011, 14:58
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JamesCH95 JamesCH95 is offline
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FRC #0095 (The Grasshoppers)
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Re: Advantage to six wheel drive?

Quote:
Originally Posted by Hawiian Cadder View Post
because a live axle is always spinning, every time there is a shock load, or the robot sits for a long period of time, the axle is in a different orientation. however ALL the shock loads on most dead axle setups occur with the axle in the same orientation. So after a while the axle may start to bend in that direction. I haven't noticed this problem with our .5 inch dead axle robot> But on the cart was made from the kit-frame, the axles are severely deformed and bent. this was also a problem on our 2009 prototype. In a year like logomotion, this may not be an issue, in a year like breakaway, where every time a robot came off the bump the axle took the shock in the same way, I think it could definitely contribute to some bending.
In some ways a dead axle would be better in the situation you described. Sure it could deform more, but the wheel wouldn't start to wobble because the shaft was bent. If the live axle was bent in one direction, then got bent back to straight, that's a fully-reversed fatigue cycle beyond the shaft's yield strength, that is BAD NEWS. The shaft is now compromised structurally, perhaps to a large degree, and will bend more easily the next time it's hit.

A dead axle bending in the same direction more and more gets stronger and stronger, until it fails of course, but these impacts are non-reversed fatigue cycles, which are better than fully-reversed fatigue cycles.
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